1. Technical Field
The present invention relates to an electro-optical device, such as a liquid crystal display device, a method of testing the electro-optical device, and an electronic apparatus including the electro-optical device.
2. Related Art
In general, electro-optical devices include an element substrate, a counter substrate, and an electro-optical material interposed therebetween. A plurality of pixels are arranged in a matrix in a pixel region (or an image display region) in plan view, and a display element including an electro-optical material is formed in each of the pixels. The counter substrate is smaller than the element substrate, that is, the element substrate protrudes from one side of the counter substrate in plan view. In a peripheral region of the pixel region, a plurality of external circuit connecting terminals are arranged along one side of the element substrate protruding from or exposed from the counter substrate. Various signals for selecting and turning on the plurality of display elements when the electro-optical device is driven, such as image signals, control signals, and power voltage signals, are supplied to the plurality of external circuit connecting terminals. For example, the electro-optical devices are manufactured by arranging a large board having the counter substrates formed thereon on a large board having a plurality of elements substrates formed thereon such that the counter substrates are opposite to the element substrates, by bonding the counter substrates to the element substrates by a sealing material, and by dividing the two large boards into a plurality of pairs of element substrates and counter substrates.
In general, test terminals to/from which test signals are input/output are provided in the peripheral region of the element substrate. The test terminals are used to test the breaking and short-circuit of circuits or wiring lines, the operation of circuits, and the operational state of the display elements when the electro-optical device is being manufactured, when it is mounted after manufacture, or before shipment.
JP-A-2004-205852 and JP-A-2004-226931 disclose an electro-optical device having the following structure: a plurality of external circuit connecting terminals are arranged along one side of the element substrate in the peripheral region and a plurality of test terminals are arranged at both ends of an array of the external circuit connecting terminals, in order to easily perform a lighting luminous test by using inexpensive test equipment. According to this structure, in the electro-optical device, the display elements performs luminous display on the basis of only the driving signals supplied from an external circuit mounted on the plurality of external circuit connecting terminals at the time of driving, and the display elements performs luminous display on the basis of only the test signals supplied to the test terminals through probes, at the time of testing. More specifically, at the time of driving, a plurality of driving signals including three types of image signals for R (red), G (green), and B (blue) are supplied, and, a plurality of test signals including three types of test image signals corresponding to these image signals are supplied at the time of testing.
Further, JP-A-2004-4993 discloses an electro-optical device having the following structure: in order to narrow a peripheral region, a plurality of test terminals are arranged at corners of a pixel region in a peripheral region of an element substrate below a sealing material for bonding an element substrate to a counter substrate so as to overlap a portion of the sealing material in plan view. The test terminals are used for a test before the element substrate and the counter substrate are bonded to each other in the manufacturing process of the electro-optical device.
However, according to the structures disclosed in JP-A-2004-20585 and JP-A-2004-226931, for example, when the image signals are supplied at the time of driving as signals whose phases are expanded into 6 phases, 12 phases, and so on by serial-to-parallel conversion, instead of three types of signals for R, G, and B, the test image signals of the type corresponding to the image signals are supplied at the time of testing. Therefore, the number of test terminals supplied with the test image signals increases, which makes it necessary to ensure a wide region for arranging the test terminals on the element substrate. That is, when the size of the element substrate is reduced, it is practically difficult to bring the probe into contact with the test terminals to perform their test.
Furthermore, according to the structure disclosed in JP-A-2004-4993, it is necessary to ensure a sufficient sealing-material-forming region to arrange a plurality of test terminals in the peripheral region of the element substrate. In addition, it is necessary to ensure a region required to arrange a driving circuit for driving a plurality of display elements on the basis of driving signals outside the region where the sealing material is formed. Also, in the manufacturing process of the electro-optical device, a region for cutting adjacent element substrates needs to be ensured around the outer periphery of each element substrate on a large board.